摘要：We present high-resolution three-dimensional tomographic images of the crust beneath the entire Kyushu arc, and particularly the western portion.Our results reveal a velocity anomaly that correlates well with an upper crustal gravity anomaly.Significant low-velocity anomalies exist beneath the Miyazaki plane and along the Beppu-Shimabara Graben.Another extensive low-velocity region near the bottom of the crust is located just below the volcanic front and between active volcanoes.The low-velocity anomalies exhibit low V p and V p / V s characteristics, and the spatial relationship between these anomalies, the Bouguer gravity anomaly, and the Moho suggests that low-density material at the base of the crust is responsible for both the seismic and gravity signatures.We interpret this material to constitute a relict ridge subducting below the Kyushu Mountains.
